Major Changes in Solr 9

Solr 9.0 is a major new release of Solr.

This page highlights the most important changes including new features and changes in default behavior as well as previously deprecated features that have now been removed.

Solr 9 Upgrade Planning

Before starting an upgrade to Solr 9, please take the time to review all information about changes from the version you are currently on up to Solr 9.

You should also consider all changes that have been made to Solr in any version you have not upgraded to already. For example, if you are currently using Solr 8.1, you should review changes made in all subsequent 8.x releases in addition to changes for 9.0.

A thorough review of the list in Major Changes in Earlier 8.x Versions as well as the CHANGES.txt in your Solr instance will help you plan your migration to Solr 9.

Upgrade Prerequisites

Solr 9 requires Java 11 as minimum Java version and is also tested with Java 17.

If using CloudSolrClient to connect to your SolrCloud cluster, SolrJ must be upgraded in all your client applications to version 8.10 or higher (8.x), before upgrading your SolrCloud cluster to version 9.0. Otherwise, SolrJ will not be able to connect to the cluster once it has upgraded to Solr 9.

If you have an old collection that was initially created with a Solr version prior to 5.0, Solr may keep that collection’s cluster state in the /clusterstate.json file at the root of Zookeeper. Solr 9 no longer supports this file. You must upgrade such collections to the new per-collection state.json format before upgrading to Solr 9. This is done by calling the Collection API MIGRATESTATEFORMAT action while still using Solr 8.x.

If you are using Solr in standalone mode with the Query Elevation Component with its elevation file in the data directory, you’ll have to move it to the configset folder instead.

If you rely on metrics, alerts, or monitors on Solr KPIs that use the "master" or "slave" terminology, please update your system for those metrics to now show up with "leader" and "follower" terminology.

Rolling Upgrades

If you are planning to upgrade your cluster using a rolling upgrade model (upgrade each node in succession, as opposed to standing up a brand new 9.x cluster), please read the following carefully.

Rolling upgrades from Solr 8 to Solr 9 require upgrading from Solr 8.7 or newer. If you run an 8.x. version prior to 8.7 we recommend that you first upgrade to 8.11.

PKI Authentication

Internode communication secured by PKI Authentication has changed formats. For detailed information, see PKI Authentication Plugin.

A rolling upgrade from Solr 8 to Solr 9 requires the following multiple restart sequence:

  1. Upgrade to Solr 9 and set system properties: solr.pki.sendVersion=v1 and solr.pki.acceptVersions=v1,v2. This will allow Solr 9 nodes to send messages to Solr 8 nodes while the upgrade is in progress.

  2. Restart with solr.pki.sendVersion=v2 (default, can be unset) and solr.pki.acceptVersions=v1,v2. This will force all nodes to send the new header.

  3. (Optional) Restart with system property solr.pki.acceptVersions=v2 (default, can be unset) to prevent outdated nodes from connecting to your cluster.

Reindexing After Upgrade

It is always strongly recommended that you fully reindex your documents after a major version upgrade. For details, see the Reindexing section, which covers several strategies for how to reindex.

In Solr 8, it was possible to add docValues to a schema without re-indexing via UninvertDocValuesMergePolicy, an advanced/expert utility. Due to changes in Lucene 9, that isn’t possible any more.

Solr 9.1

Querying and Indexing

  • Added Lucene91HnswVectorsFormat codec for DenseVectorField. In order to use the new codec, reindex is necessary.

SolrJ

SolrJ is beginning to be split up. If you use ZooKeeper coordinates to create a CloudSolrClient, you will need to add a dependency on solrj-zookeeper. If you use SolrJ’s Maven POM to depend on SolrJ, then this should happen automatically through transitive resolution. Instead of depending on ZooKeeper, consider migrating to use of specifying a list of Solr URLs in the client’s builder. Not only does this reduce dependencies, but it improves security by being able to limit ZooKeeper access.

Solr 9.0

Querying and Indexing

  • Dense Vector "Neural" Search through DenseVectorField fieldType and K-Nearest-Neighbor (KNN) Query Parser.

  • Admin UI support for SQL Querying.

  • New snowball stemmers: Hindi, Indonesian, Nepali, Serbian, Tamil, and Yiddish.

  • New NorwegianNormalizationFilter

  • Implicit /terms handler now returns terms across all shards in SolrCloud instead of only the local core. Users/apps may be assuming the old behavior. A request can be modified via the standard distrib=false param to only use the local core receiving the request.

  • SQL support has been moved to the sql module. Existing Solr configurations do not need any SQL related changes, however the module needs to be installed - see the section SQL Query Language.

  • JSON aggregations uses corrected sample formula to compute standard deviation and variance. The computation of stdDev and variance in JSON aggregation is same as StatsComponent.

  • Facet count in Json Facet module always returns a long value, irrespective of number of shards.

  • MacroExpander will no longer will expand URL parameters inside of the expr parameter (used by streaming expressions). Additionally, users are advised to use the InjectionDefense class when constructing streaming expressions that include user supplied data to avoid risks similar to SQL injection. The legacy behavior of expanding the expr parameter can be reinstated with -DStreamingExpressionMacros=true passed to the JVM at startup

  • The response format for field values serialized as raw XML (via the [xml] raw value DocTransformer and wt=xml) has changed. Previously, values were dropped in directly as top-level child elements of each <doc>, obscuring associated field names and yielding inconsistent <doc> structure. As of version 9.0, raw values are wrapped in a <raw name="field_name">[…​]</raw> element at the top level of each <doc> (or within an enclosing <arr name="field_name"><raw>[…​]</raw></arr> element for multi-valued fields). Existing clients that parse field values serialized in this way will need to be updated accordingly.

  • Highlighting: hl.method=unified is the new default. Use hl.method=original to switch back if needed.

  • solr.xml maxBooleanClauses is now enforced recursively. Users who upgrade from prior versions of Solr may find that some requests involving complex internal query structures (Example: long query strings using edismax with many qf and pf fields that include query time synonym expansion) which worked in the past now hit this limit and fail. Users in this situation are advised to consider the complexity of their queries/configuration, and increase the value of maxBooleanClauses if warranted.

  • Atomic/partial updates to nested documents now require the _root_ field to clearly show the document isn’t a root document. Solr 8 would fallback on the _route_ param but no longer.

Security

  • New Certificate Authentication Plugin, enabling end-to-end use of x509 client certificates for Authentication and Authorization.

  • Improved security when using PKI Authentication plugin.

  • Upgrade to Zookeeper 3.7, allowing for TLS protected ZK communication.

  • All request handlers support security permissions. Users may have to adapt their security.json.

  • Ability to disable admin UI through a system property.

  • The property blockUnknown in the BasicAuthPlugin and the JWTAuthPlugin now defaults to true instead of false. This change is backward incompatible. If you need the pre-9.0 default behavior, you need to explicitly set blockUnknown:false in security.json.

  • Solr now runs with the Java security manager enabled by default. Hadoop users may need to disable this.

  • Solr now binds to localhost network interface by default for better out of the box security. Administrators that need Solr exposed more broadly can change the SOLR_JETTY_HOST property in their Solr include (solr.in.sh/solr.in.cmd) file.

  • Solr embedded zookeeper only binds to localhost by default. This embedded zookeeper should not be used in production. If you rely upon the previous behavior, then you can change the clientPortAddress in solr/server/solr/zoo.cfg

  • Jetty low level request-logging in NCSA format is now enabled by default, with a retention of 3 days worth of logs. This may require some more disk space for logs than was the case in version 8.x. See Configuring Logging for how to change this.

  • Hadoop authentication support has been moved to the new hadoop-auth module. Existing Solr configurations do not need any Hadoop authentication related changes, however the module needs to be installed - see the section Hadoop Authentication Plugin.

  • JWTAuthPlugin has been moved to a module. Users need to add the module jwt-auth to classpath. The plugin has also changed package name to org.apache.solr.security.jwt, but can still be loaded as shortform class="solr.JWTAuthPlugin".

  • Dependency updates - A lot of dependency updates removes several security issues from dependencies, and thus make Solr more secure.

  • The allow-list defining allowed URLs for the shards parameter is not in the shardHandler configuration anymore. It is defined by the allowUrls top-level property of the solr.xml file. For more information, see Format of solr.allowUrls documentation.

  • To improve security, StatelessScriptUpdateProcessorFactory has been renamed as ScriptUpdateProcessorFactory and moved to the scripting Module instead of shipping as part of Solr core. This module needs to be enabled explicitly.

  • To improve security, XSLTResponseWriter has been moved to the scripting Module instead of shipping as part of Solr core. This module needs to be enabled explicitly.

Stability and Scalability

  • Rate limiting provides a way to throttle update and search requests based on usage metrics.

  • A new Task management interface allows declaring tasks as cancellable and trackable.

  • Ability to specify node roles in Solr. This release supports overseer and data roles out of the box.

  • New API for pluggable Replica Placement Plugins that replaces the auto-scaling framework.

  • Support for distributed processing of cluster state updates and collection API calls, without relying on the Overseer.

Build and Docker

  • Solr is now built and released independently of Lucene (separate Apache projects).

  • Build system switched to Gradle, no longer uses Ant + Ivy.

  • Docker image creation is now a part of the Apache Solr GitHub repo.

  • Docker image documentation is now a part of the reference guide.

  • Official Docker image upgraded to use JDK17 (by Eclipse Temurin) and ability to create functionally identical local image.

Logging and Metrics

  • Metrics handler only depends on SolrJ instead of core and has its own log4j2.xml and no longer shares Solr’s logging config.

  • Only SearchHandler and subclasses have "local" metrics now. It’s now tracked as if it’s another handler with a "[shard]" suffix, e.g. "/select[shard]". There are no longer ".distrib." named metrics; all metrics are assumed to be such except "[shard]". The default Prometheus exporter config splits that component to a new label named "internal". The sample Grafana dashboard now filters to include or exclude this.

  • The default port of "Prometheus exporter" has changed from 9983 to 8989, so you may need to adjust your configuration after upgrade.

  • Logging is now asynchronous by default. There’s a small window where log messages may be lost in the event of some hard crash. Switch back to synchronous logging if this is unacceptable, see comments in the log4j2 configuration files (log4j2.xml by default).

  • Log4J configuration & Solr MDC values - MDC values that Solr sets for use by Logging calls (such as the collection name, shard name, replica name, etc…​) have been modified to now be "bare" values, without the special single character prefixes that were included in past version. The default log4j2.xml configuration file for Solr has been modified to prepend these same prefixes to MDC values when included in Log messages as part of the <PatternLayout/>. Users who have custom logging configurations that wish to ensure Solr 9.x logs are consistently formatted after upgrading will need to make similar changes to their logging configuration files. See SOLR-15630 for more details.

  • Jetty Request log is now enabled by default, i.e. logging every request.

  • The prometheus-exporter is no longer packaged as a Solr Module. It can be found under solr/prometheus-exporter/.

  • Solr modules (formerly known as contribs) can now easily be enabled by an environment variable (e.g. in solr.in.sh or solr.in.cmd) or as a system property (e.g. in SOLR_OPTS). Example: SOLR_MODULES=extraction,ltr.

Deprecations and Removals

  • The Data Import Handler (DIH) is an independent project now; it is no longer a part of Solr.

  • No more support for clusterstate.json and MIGRATESTATE API has been removed. If your collections use clusterstate.json you will need to take some steps, described elsewhere in this document.

  • Auto-scaling framework has been removed. Please refer to Replica Placement Plugins for alternate options.

  • LegacyBM25SimilarityFactory has been removed.

  • Legacy SolrCache implementations (LRUCache, LFUCache, FastLRUCache) have been removed. Users have to modify their existing configurations to use CaffeineCache instead.

  • VelocityResponseWriter is an independent project now; it is no longer a part of Solr. This encompasses all previously included /browse and wt=velocity examples.

  • Cross Data Center Replication has been removed.

  • SolrJ clients like HttpSolrClient and LBHttpSolrClient that lacked HTTP2 support have been deprecated. The old CloudSolrClient has been renamed as CloudLegacySolrClient and deprecated.

  • SimpleFSDirectoryFactory is removed in favor of NIOFSDirectoryFactory

  • Removed the deprecated HttpSolrClient.RemoteSolrException and HttpSolrClient.RemoteExecutionException. All the usages are replaced by BaseHttpSolrClient.RemoteSolrException and BaseHttpSolrClient.RemoteExecutionException.

  • maxShardsPerNode parameter has been removed because it was broken and inconsistent with other replica placement strategies. Other relevant placement strategies should be used instead, such as autoscaling policy or rules-based placement.

  • The binary distribution no longer contains test-framework jars.

  • Deprecated BlockJoinFacetComponent and BlockJoinDocSetFacetComponent are removed. Users are encouraged to migrate to uniqueBlock() in JSON Facet API.

  • Core level admin API endpoints /admin/threads, /admin/properties, /admin/logging are now only available at the node level.

Other

  • Contrib modules are now just "modules". You can easily enable module(s) through environment variable SOLR_MODULES.

  • Features lifted out as separate modules are: HDFS, Hadoop-Auth, SQL, Scripting, and JWT-Auth.

  • The "dist" folder in the release has been removed. Please update your <lib> entries in your solrconfig.xml to use the new location.

    • The solr-core and solr-solrj jars can be found under server/solr-webapp/webapp/WEB-INF/lib/.

    • The Solr Module jars and their dependencies can be found in modules/<module-name>/lib, packaged individually for each module.

    • The solrj-deps (SolrJ Dependencies) are no longer separated out from the other Server jars.

    • Please refer to the SolrJ Maven artifact to see the exact dependencies you need to include from server/solr-webapp/webapp/WEB-INF/lib/ and server/lib/ext/ if you are loading in SolrJ manually. If you plan on using SolrJ as a JDBC driver, please refer to the JDBC documentation

    • More information can be found in the Libs documentation.

  • SolrJ class CloudSolrClient now supports HTTP2. It has a new Builder. See CloudLegacySolrClient for the 8.x version of this class.

  • In Backup request responses, the response key now uses a map to return information instead of a list. This is only applicable for users returning information in JSON format, which is the default behavior.

  • SolrMetricProducer / SolrInfoBean APIs have changed and third-party components that implement these APIs need to be updated.

  • Use of blacklist/whitelist terminology has been completely removed. JWTAuthPlugin parameter algWhitelist is now algAllowlist. The old parameter will still work in 9.x. Environment variables SOLR_IP_WHITELIST and SOLR_IP_BLACKLIST are no longer supported, but replaced with SOLR_IP_ALLOWLIST and SOLR_IP_DENYLIST.

  • Solr Backups - Async responses for backups now correctly aggregate and return information. For collection’s snapshot backup request responses additional fields indexVersion, indexFileCount, etc. were added similar to incremental backup request responses.

  • If you are using the HDFS backup repository, you need to change the repository class to org.apache.solr.hdfs.backup.repository.HdfsBackupRepository - see the HDFS Backup Repository section.

  • HDFS storage support has been moved to a module. Existing Solr configurations do not need any HDFS-related changes, however the module needs to be installed - see the section Solr on HDFS.

  • The folder $SOLR_HOME/userfiles, used by the "cat" streaming expression, is no longer created automatically on startup. The user must create this folder.

  • Solr no longer requires a solr.xml in $SOLR_HOME. If one is not found, Solr will instead use the default one from $SOLR_TIP/server/solr/solr.xml. You can revert to the pre-9.0 behaviour by setting environment variable SOLR_SOLRXML_REQUIRED=true or system property -Dsolr.solrxml.required=true. Solr also does not require a zoo.cfg in $SOLR_HOME if started with embedded zookeeper.

  • base_url has been removed from stored cluster state. If you’re able to upgrade SolrJ to 8.8.x for all of your client applications, then you can set -Dsolr.storeBaseUrl=false (introduced in Solr 8.8.1) to better align the stored state in Zookeeper with future versions of Solr; as of Solr 9.x, the base_url will no longer be persisted in stored state. However, if you are not able to upgrade SolrJ to 8.8.x for all client applications, then you should set -Dsolr.storeBaseUrl=true so that Solr will continue to store the base_url in Zookeeper. For background, see: SOLR-12182 and SOLR-15145. Support for the solr.storeBaseUrl system property will be removed in Solr 10.x and base_url will no longer be stored.

  • Analyzer components can now be looked up by their SPI names based on the field type configuration.

  • The solr-extraction module has been cleaned up to produce solr-extraction- jar instead of solr-cell- jars.

  • Extra lucene libraries used in modules are no longer packaged in lucene-libs/ under module directories in the binary release. Instead, these libraries will be included with all other module dependencies in lib/.

Major Changes in Earlier 8.x Versions

The following is a list of major changes released between Solr 8.1 and 8.11.

Please be sure to review this list so you understand what may have changed between the version of Solr you are currently running and Solr 9.0.

Solr 8.11

See the 8.11 Release Notes for an overview of the main new features of Solr 8.11.

When upgrading to 8.11.x users should be aware of the following major changes from 8.10.

Support for Multiple Authentication Schemes

Two new authentication and authorization plugins provide support for configuring multiple authentication schemes.

The MultiAuthPlugin allows combining two or more authentication approaches, such as JWT and Basic authentication.

The MultiAuthRuleBasedAuthorizationPlugin is used when the MultiAuthPlugin is also in use, and combines the various roles defined for all plugins to determine the proper role assignment for the user account.

For information on configuring these plugins, see the following sections:

ZooKeeper chroot

It’s now possible to create the ZooKeeper chroot at startup if it does not already exist. See the section Using the -z Parameter with bin/solr for an example.

Other Changes

A few other minor changes are worth noting:

  • The config-read pre-defined permission now correctly governs access for various configuration-related APIs. See also Predefined Permissions.

  • The S3BackupRepository supports configuring the AWS Profile, if necessary. See also S3BackupRepository.

  • Additionally, backups will now properly succeed after SPLITSHARD operations, and will correctly handle incremental backup purges.

  • SolrJ now supports uploading configsets.

Solr 8.10

See the 8.10 Release Notes for an overview of the main new features of Solr 8.10.

When upgrading to 8.10.x users should be aware of the following major changes from 8.9.

Schema Designer UI

A new screen has been added to the Admin UI that allows you to interactively design a Solr schema using your documents.

The designer screen provides a safe environment for you to:

  • Upload or paste sample documents to identify fields.

  • Get a "first" guess at what Solr thinks the field types in the fields should be.

  • Edit fields, field types, dynamic fields, and supporting files.

  • See how a field’s analysis will impact your text.

  • Test how schema changes will impact query-time behavior.

  • Save your changes to a configset to use with a new collection.

See the section Schema Designer for full details.

Backups in S3

Following the redesign of backups in Solr 8.8 that allowed storage of incremental backups in Google Cloud environments, Solr 8.10 provides support for storing backups in Amazon S3 buckets.

See the section S3BackupRepository for how to configure.

Security Admin UI

Solr’s Admin UI also got a new screen to support management of users, roles, and permissions.

The new UI works when authentication and/or authorization has been enabled with bin/solr auth or by manually installing a security.json file. Before this, it provides a warning that your Solr instance is unsecured.

See the section Security UI for details.

Solr SQL Improvements

A number of improvements have been made in Solr’s SQL functionality:

  • Support added for LIKE, IS NOT NULL, IS NULL, and wildcards (for simplistic LIKE functionality).

  • Two new aggregation functions, COUNT(DISTINCT field) and APPROX_COUNT_DISTINCT(field), have been added.

  • Queries using an ORDER BY clause can support OFFSET and FETCH operations.

  • Multi-valued fields can now be returned.

  • User permissions have been simplified so access to query endpoints /sql, /select, and /export is sufficient for full access for all SQL queries.

shards.preference

A new option for the shards.preference parameter allows selection of nodes based on whether or not the replica is a leader. Now adding shards.preference=replica.leader:false will limit queries only to replicas which are not currently their shard’s leader.

See the section shards.preference Parameter for details and examples.

Metrics & Prometheus Exporter

A new expr option in the Metrics API allows for more advanced filtering of metrics based on regular expressions. See the section Metrics API for examples.

The Prometheus Exporter’s default solr-exporter.config has been improved to use the new expr option in the Metrics API to get a smaller set of metrics. The default metrics exported still include most metrics, but the configuration will be easier to trim as needed. This should help provide performance improvements in busy clusters being monitored by Prometheus.

ZooKeeper Credentials

ZooKeeper credentials can now be stored in a file whose location is defined with a system property instead of being passed in plain-text. See Out of the Box Credential Implementations for how to set this up.

Solr 8.9

See the 8.9 Release Notes for an overview of the main new features of Solr 8.9.

When upgrading to 8.9.x users should be aware of the following major changes from 8.8.

Backup and Restore

Solr 8.9 introduces extensive changes to Solr’s backup and restore support.

A new backup format has been introduced in Solr 8.9 which replaces the previous snapshot-based backup. This new format enables ‘incremental’ backups. Repeated backups to a given location will take advantage of the data stored by their predecessors and will only operate on files that have changed since the previous backup. This is supported by default, simply by storing each backup file in the same location.

The old and new formats are not compatible, although backups in the old format, a full snapshot of all files, can still be used to restore to Solr for the time-being. The old format is officially deprecated, and support for it is likely to be removed in Solr 9.0.

For the time-being the old format can be created by defining a parameter incremental=false. Again, though, this support is likely to be removed in Solr 9.0.

More documentation on backups is available at Backup and Restore.

New Collections API commands for backups:

  • LISTBACKUP: Lists information about each backup stored at the specified repository location. See List Backups for more details.

  • DELETEBACKUP: Deletes specified backups from the repository. See Delete Backups for more details.

A new option for backup repository is also available in 8.9, which is to use Google Cloud Storage (GCS). This is a module (located in modules/gcs-repository). See GCSBackupRepository for configuration details. The Solr community is working to add support for S3 buckets in the near future.

Nested Docs

Child Doc Transformer’s childFilter parameter no longer applies query syntax escaping because it’s inconsistent with the rest of Solr and was limiting. This refers to [child childFilter='field:value']. There was no escaping here prior to 8.0 either.

Collapse and Expand

  • BlockCollapse: If documents have been (or could be) indexed in a way where documents with the same collapse key have been indexed contiguously in the index, a new "block collapse" provides a significant speed improvement over traditional collapse.

    See Block Collapsing for details.

  • Expand Null Groups: A new parameter expand.nullGroup allows an expanded group to be returned containing document with no value in the expanded field. See Expand Component for details.

In-Place Updates

A new request parameter update.partial.requireInPlace=true allows telling Solr to "fail fast" if all of the necessary conditions are not satisfied to allow an in-place update to succeed. See also In-Place Updates.

Metrics History

The Metrics History feature, which allowed long-term storage and aggregation of Solr’s metrics, has been deprecated and will be removed in 9.0.

Embedded Solr Server

When using EmbeddedSolrServer, it will no longer close CoreContainer instances that were passed to it.

Solr 8.8

When upgrading to 8.8.x users should be aware of the following major changes from 8.7.

Nested Documents

  • When doing atomic/partial updates to a child document:

    • Supply the _root_ field (the ID of the root document) so that Solr understands you are manipulating a child document and not a root document. In its absence, Solr looks at the _route_ parameter but this may change in the future because it’s not an ideal substitute. If neither are present, Solr assumes you are updating a root document. If this assumption is false, Solr will do a cheap check that usually detects the problem and will throw an exception to alert you of the need to specify the Root ID. This backwards incompatible change was done to increase performance and robustness.

    • This feature no longer requires stored=true or docValues=true on the _root_ field. You might have it for other purposes though (e.g., for uniqueBlock(…​)).

    • This feature no longer requires the _nest_path_ field, although you probably ought to continue to define it as it’s useful for other things.

Removed Modules

  • The search results clustering module (Carrot2) has been removed from 8.x Solr due to lack of Java 1.8 compatibility in the dependency that provides online clustering of search results. The module will be re-introduced in Solr 9.0.

Learning to Rank

Metrics

  • Two metrics have been added for SolrCloud’s Overseer:

    • solr_metrics_overseer_stateUpdateQueueSize

    • solr_metrics_overseer_collectionWorkQueueSize

Prometheus Exporter

  • The ./bin scripts included with the Prometheus Exporter now allow use of custom java options with environment variables. See the section Environment Variable Options for more details.

  • The default Grafana dashboards now include panels for query performance monitoring. The default Prometheus Exporter configuration includes metrics like queries-per-second (QPS) and 95th percentiles (P95) to populate the new panels.

  • The default Prometheus Exporter configuration also includes the two new metrics mentioned in the Metrics above.

Solr Home

  • The internal logic for identifying 'Solr Home' (solr.solr.home) has been refactored to make testing less error-prone. Plugin developers using SolrPaths.locateSolrHome() or new SolrResourceLoader should check deprecation warnings as existing some existing functionality will be removed in 9.0. SOLR-14934 has more technical details about this change for those concerned.

base_url removed from stored state

As of Solr 8.8.0, the base_url property was removed from the stored state for replicas (SOLR-12182). If you’re able to upgrade SolrJ to 8.8.x for all of your client applications, then you can set -Dsolr.storeBaseUrl=false (introduced in Solr 8.8.1) to better align the stored state in ZooKeeper with future versions of Solr. However, if you are not able to upgrade SolrJ to 8.8.x for all client applications, then leave the default -Dsolr.storeBaseUrl=true so that Solr will continue to store the base_url in ZooKeeper.

You may also see some NPE in collection state updates during a rolling upgrade to 8.8.0 from a previous version of Solr. After upgrading all nodes in your cluster to 8.8.0, collections should fully recover. Trigger another rolling restart if there are any replicas that do not recover after the upgrade to re-elect leaders.

Solr 8.7

See the 8.7 Release Notes for an overview of the main new features of Solr 8.7.

When upgrading to 8.7.x users should be aware of the following major changes from 8.6.

Autoscaling

  • If upgrading from 8.6.0, please see the 8.6.1 Upgrade notes below for information on performance degradations introduced in 8.6.0 that require some intervention to resolve. If you are already on 8.6.1 or higher, you can ignore these instructions.

Deprecations

  • The autoscaling framework is now formally deprecated and will be removed in Solr 9.0. The Solr community is working on pluggable API to replace this functionality, with the goal for it to be ready by the time 9.0 is released. Deprecations include: autoscaling policy, triggers, withCollection support, simulation framework, autoscaling suggestions tab in the UI, autoAddReplicas and UTILIZENODE command.

  • Similarly, rule-based replica placement strategy has been deprecated and will be replaced in Solr 9.0 by APIs for replica placement and cluster events, with plugin-based implementations.

  • Support for detecting spinning disks has been removed in LUCENE-9576. Corresponding spins metrics in Solr still exist but now they always return false and will be removed in Solr 9.0.

User-Managed Cluster Terminology Updated

  • Solr has replaced the terms "master" and "slave" in the codebase and all documentation with "leader" and "follower".

    This functionality has only changed in terms of parameter names changed, and we do not expect any back-compatibility issues on upgrade to 8.7 or even 9.0 later.

    However, users should update their solrconfig.xml files after completing the upgrade on all nodes of a cluster. Comparing your configuration to the updated configuration examples in User-Managed Index Replication will show examples of what needs to change, but here are the main changes:

    1. On the replication leader, in the definition of the /replication request handler:

      1. Replace "master" with "leader".

      2. Replace "slave" with "follower" if the former term is used in the name of any follower solrconfig.xml file definitions. This file can be named anything, so you can change it to whatever you’d like to call it if you’d like.

      3. Replace "slave" with "follower" if the former term is used in a replication repeater configuration.

    2. On the replication follower, in the definition of the /replication request handler:

      1. Replace "masterUrl" with "leaderUrl".

      2. Replace "slave" with "follower" if the former term is used in a repeater configuration.

JSON Facets

  • Performance enhancements for the relatedness() statistics function are included with 8.7. These yield the highest benefits with high-cardinality fields and can be disabled if working with lower cardinality fields with a new sweep_collection parameter. See the section relatedness() Options for details.

solr.in.sh / solr.in.cmd

  • Solr has relied on the SOLR_STOP_WAIT parameter defined in solr.in.sh or solr.in.cmd to determine how long to wait on startup. A new parameter SOLR_START_WAIT allows defining how long Solr should wait for start up to complete.

    If the time set by this parameter is exceeded, Solr will exit the startup process and return the last few lines of the solr.log file to the terminal.

    By default, this parameter is set to the same value as SOLR_STOP_WAIT.

  • The default ZooKeeper client timeout (ZK_CLIENT_TIMEOUT) is now 30 seconds (30000 milliseconds) instead of 15.

Configsets

  • It’s now possible to overwrite an existing configset when uploading changes by supplying the overwrite=true parameter to the Configset API.

    A related parameter is cleanup=true, which allows deleting any files from the old configset that are left behind after the overwrite.

    The default for both of these parameters is false.

  • When deleting a collection that has an automatically created configset (i.e., the configset was copied from the _default collection when the collection was created), the configset will also be deleted if it is not in use by any other collection.

Logging

  • A request ID (rid) is now logged for all distributed search requests (in SolrCloud) which can be used to correlate query events across the system. A parameter disableRequestId=true can be added to disable this if desired.

Solr 8.6.1

See the 8.6.1 Release Notes for an overview of the fixes included in Solr 8.6.1.

When upgrading to 8.6.1 users should be aware of the following major changes from 8.6.0.

Autoscaling

  • As mentioned in the 8.6 upgrade notes, a default autoscaling policy was provided starting in 8.6.0. This default autoscaling policy resulted in increasingly slow collection creation calls in large clusters (50+ collections).

    In 8.6.1 the default autoscaling policy has been removed, and clusters will not use autoscaling unless a policy has explicitly been created. If your cluster is running 8.6.0 and not using an explicit autoscaling policy, upgrade to 8.6.1 and remove the default cluster policy and preferences via the following command.

    Replace localhost:8983 with your Solr endpoint.

    curl -X POST -H 'Content-type:application/json'  -d '{set-cluster-policy : [], set-cluster-preferences : []}' http://localhost:8983/api/cluster/autoscaling

    This information is only relevant for users upgrading from 8.6.0. If upgrading from an earlier version to 8.6.1+, this warning can be ignored.

Solr 8.6

See the 8.6 Release Notes for an overview of the main new features of Solr 8.6.

When upgrading to 8.6.x users should be aware of the following major changes from 8.5.

Support for Block-Max WAND

Lucene added support for Block-Max WAND in 8.0, and 8.6 makes this available for Solr also.

This can provide significant performance enhancements by not calculating the score for results which are not likely to appear in the top set of results.

It is enabled when using a new query parameter minExactCount. This parameter tells Solr to accurately count the number of hits accurately until at least this value. Once this value is reached, Solr can skip over documents that don’t have a score high enough to be in the top set of documents, which has the potential for greatly speeding up searches.

It’s important to note that when using this parameter, the hit count of searches may not be accurate. It is guaranteed that the hit count is accurate up to the value of minExactCount, but any returned hit count higher than that may be an approximation.

A new boolean attribute numFoundExact is included in all responses to indicate if the hit count in the response is expected to be exact or not.

More information about this new feature is available in the section minExactCount Parameter.

Autoscaling

  • NOTE: The default autoscaling policy has been removed as of 8.6.1

    Solr now includes a default autoscaling policy. This policy can be overridden with your custom rules or by specifying an empty policy to replace the default.

  • The ComputePlan action now supports a collection selector to identify collections based on collection properties to determine which collections should be operated on.

Security

  • Prior to Solr 8.6 Solr APIs which take a file system location, such as core creation, backup, restore, and others, did not validate the path and Solr would allow any absolute or relative path. Starting in 8.6 only paths that are relative to SOLR_HOME, SOLR_DATA_HOME and coreRootDir are allowed by default.

    If you need to create a core or store a backup outside the default paths, you will need to tell Solr which paths to allow. A new element in solr.xml called allowPaths takes a comma-separated list of allowed paths.

    When using the solr.xml file that ships with 8.6, you can configure the list of paths to allow through the system property solr.allowPaths. Please see bin/solr.in.sh or bin\solr.in.cmd for example usage. Using the value * will allow any path as in earlier versions.

    For more on this, see the section Solr.xml Parameters.

    Windows SMB shares on the UNC format, such as \\myhost\myshare\mypath are now always disallowed. Please use drive letter mounts instead, i.e., S:\mypath.

  • A new authorization plugin ExternalRoleRuleBasedAuthorizationPlugin is now available. This plugin allows an authentication plugin (such as JWT) to supply a user’s roles instead of maintaining a user-to-role mapping inside Solr.

  • When authentication is enabled, the Admin UI Dashboard (main screen) now includes a panel that shows the authentication and authorization plugins in use, the logged in username, and the roles assigned to this user. A new link will also appear in the left-hand navigation to allow a user to log out.

Streaming Expressions

  • The /export handler now supports streaming expressions to allow limiting the output of the export to only matching documents.

    For more information about how to use this, see the section Specifying the Local Streaming Expression.

  • The stats, facet, and timeseries expressions now support percentiles and standard deviation aggregations.

Highlighting

For the Unified Highlighter: The setting hl.fragsizeIsMinimum now defaults to false because true was found to be a significant performance regression when highlighting lots of text. This will yield longer highlights on average compared to Solr 8.5 but relatively unchanged compared to previous releases. Furthermore, if your application highlights lots of text, you may want to experiment with lowering hl.fragAlignRatio to trade ideal fragment alignment for better performance.

Deprecations

A primary focus of the community is improving Solr’s stability and supportability. With the addition of the package manager system in 8.4, we now have the ability to move some features into plugins maintained by third-parties with the expertise to properly develop and support them. Our goal is to make running Solr easier and less prone to outages and other headaches. In this spirit, the following features have been deprecated and are slated to be removed in Solr 9.0.

  • Cross Data Center Replication (CDCR), in its current form, is deprecated and is scheduled to be removed in 9.0. This feature is unlikely to be replaced by an identical plugin. However, the community is working on figuring out a replacement feature for disaster recovery and failover.

  • The Data Import Handler (DIH) is deprecated and is scheduled to be removed in 9.0. Work to replace DIH with a community-supported plugin is underway and may be available soon.

  • Support to store indexes and backups in HDFS is deprecated and is scheduled to be removed in 9.0. A community-supported version of this may be available as a plugin in the future. For more details, please see SOLR-14021.

Users interested in maintaining a feature as a plugin are encouraged to join the developer mailing list to find out more about how to help.

Solr 8.5

See the 8.5 Release Notes for an overview of the main new features of Solr 8.5.

When upgrading to 8.5.x users should be aware of the following major changes from 8.4.

Note: an index incompatibility warning was retroactively added below to 8.4 for users choosing a non-default postings format (e.g., "FST50").

Considerations for a SolrCloud Upgrade

Solr 8.5 introduces a change in the format used for the elements in the Overseer queues and maps (see SOLR-14095 for technical discussion of the change). This queue is used internally by the Overseer to reliably handle operations, to communicate operation results between the Overseer and the coordinator node, and by the REQUESTSTATUS API for displaying information about async Collection operations.

This change won’t require you to change any client-side code you should see no differences on the client side. However, it does require some care when upgrading an existing SolrCloud cluster depending on your upgrade strategy.

If you are upgrading Solr with an atomic restart strategy:

  • If you don’t use async or REQUESTSTATUS operations, you should be able to restart and not see any issues.

  • If you do use Collection API operations:

    1. Pause Collection API operations.

    2. Cleanup queues (See the section DELETESTATUS for examples) if you use async operations.

    3. Upgrade and restart the nodes.

    4. Resume all normal operations.

If you are upgrading Solr with a rolling restart strategy:

  • If you don’t use Collection API operations, you should be able to do a rolling restart and not see any issues.

  • If you do use Collection API operations, but you can pause their use during the restart the easiest way is to:

    1. Pause Collection API operations.

    2. Upgrade and restart all nodes.

    3. Cleanup queues (See the section DELETESTATUS for examples) if you use async operations.

    4. Resume all normal operations.

If you use Collection API operations and can’t pause them during the upgrade:

  1. Start 8.5 nodes with the system property: -Dsolr.useUnsafeOverseerResponse=deserialization. Ensure the Overseer node is upgraded last.

  2. Once all nodes are in 8.5 and once you don’t need to read old status anymore, restart again removing the system property.

If you prefer to keep the old (but insecure) serialization strategy, you can start your nodes using the system property: -Dsolr.useUnsafeOverseerResponse=true. Keep in mind that this will be removed in future version of Solr.

Security Manager

Solr now has the ability to run with a Java security manager enabled. To enable this, set the property SOLR_SECURITY_MANAGER_ENABLED=true in solr.in.sh or solr.in.cmd. Note that if you are using HDFS to store indexes, you cannot enable the security manager.

In Solr 9.0, this will be the default.

Block/Allow Specific IPs

Solr has two new parameters to allow you to restrict access to Solr using IP addresses. Use SOLR_IP_WHITELIST to configure a whitelist, and SOLR_IP_BLACKLIST to configure a blacklist. These properties are defined in solr.in.sh or solr.in.cmd.

See also the section Enable IP Access Control.

BlockJoin Facet Deprecation

The BlockJoinFacetComponent is marked for deprecation and will be removed in 9.0. Users are encouraged to migrate to uniqueBlock() in JSON Facet API. More information about this is available in the section Block Join Domain Changes.

Caching with the Boolean Query Parser

By default, the Boolean Query Parser caches queries in Solr’s filterCache. It’s now possible to disable this with the local param cache=false.

Indexing Log Files

Solr now includes a command line tool, bin/postlogs which will index Solr’s log files into a collection. This provides an easy way to use Solr or visualization tools (such as Zeppelin) to troubleshoot problems with the system.

See the documentation for more details at Log Analytics.

Highlighting

Solr’s Unified Highlighter now has two parameters to help control passage sizing, hl.fragAlignRatio and hl.fragsizeIsMinimum. See the section Unified Highlighter for details about these new parameters. Regardless of the settings, the passages may be sized differently than before. Warning: These default settings were found to be a significant performance regression for apps that highlight lots of text with the default sentence break iterator. See the 8.6 upgrade notes for advise you can apply in 8.5.

Shared Library System Parameter

Solr’s solr.xml file has long had support for a sharedLib parameter, which allows you to define a common location for .jar files that may need to be in the path for all cores.

This property can now be defined in solr.in.sh or solr.in.cmd as a system property (-Dsolr.sharedLib=/path/to/lib) added to SOLR_OPTS (see solr.in.sh or solr.in.cmd for details).

Solr 8.4

See the 8.4 Release Notes for an overview of the main new features of Solr 8.4.

When upgrading to 8.4.x users should be aware of the following major changes from 8.3.

Reminder: If you set the postingsFormat or docValuesFormat in the schema in order to use a non-default option, you risk preventing yourself from upgrading your Lucene/Solr software at future versions. Multiple non-default postings formats changed in 8.4, thus rendering the index data from a previous index. This includes "FST50" which was recommended by the Solr TaggerHandler for performance reasons. There is now improved documentation to navigate this trade-off choice.

Package Management System

Version 8.4 introduces a package management system to Solr. The goals of the system are to allow hot (live) deployment of plugins, provide packaging guidelines for plugins, and standardize Solr’s approach by following familiar concepts used in other package management systems.

The system is designed to eventually replace use of the <lib ../> directive, the Blob Store, and other methods of deploying plugins and custom components to Solr.

The system is currently considered experimental, so use with caution. It must be enabled with a system parameter passed at start up before it can be used. For details, please see the section Package Management.

With this feature Solr’s Blob Store functionality is now deprecated and will likely be removed in 9.0.

Security

The follow mix of changes were all made with the intention of making Solr more secure out of the box.

  • The solrconfig.xml file in Solr’s _default configset has been trimmed of the following previously pre-configured items:

    • All <lib …​/> directives. This means that Solr Cell (aka Tika), Learning to Rank, Clustering (with Carrot2), language identification, and Velocity (for the /browse sample search interface) are no longer enabled out of the box.

    • The /browse, /tvrh, and /update/extract request handlers.

    • The Term Vector Component.

    • The XSLT and Velocity response writers.

      All of these items can be added to your Solr implementation by manually editing solrconfig.xml to add them back in, or use the Config API.

      The sample_techproducts_configs and the examples found in ./example are unchanged.

  • Configsets that have been uploaded with an unsecured Configset API (i.e., when authentication is not enabled) are considered "Untrusted Configsets".

    In order to bolster Solr’s out-of-the-box security, these untrusted configsets are no longer allowed to use the <lib …​/> directive to implement modules or custom Jars.

    When upgrading to 8.4, if you are using untrusted configsets that contain <lib ../> directives, their corresponding collections will not load (they will cease to work). You have a few options in this case:

    • You can secure your Solr instance with authentication and re-upload the configset (using the bin/solr zk upconfig …​ Solr CLI command);

    • You can put your custom Jars in Solr’s classpath instead of lib directories;

    • You can try the new package management system to manage your custom Jars.

      See the section Upload a Configset for more details about trusted vs. untrusted configsets.

  • Our default Jetty configuration has been updated to now set a Content-Security-Policy (CSP) by default. See ./server/etc/jetty.xml for details about how it is configured.

    As a result of this change, any custom HTML served by Solr’s HTTP server that contains inline Javascript will no longer execute in modern browsers. The options for you are:

    • Change your JavaScript code to not run inline any longer;

    • Edit jetty.xml to remove CSP (creating weaker security protection);

    • Remove/alter the headers with a reverse proxy.

  • Solr’s Blob Store and runtime libs functionality are now deprecated and are planned to be removed from Solr in version 9.0. It has been replaced with the new package management system.

  • The Velocity response writer is also now deprecated and is planned to be removed from Solr in version 9.0.

Using Collapse with Group Disallowed

Using the CollapsingQueryParser with Result Grouping has never been supported as it causes inconsistent behavior and NullPointerException errors. We have now explicitly disallowed this combination to prevent these errors. If you are using these together, you will need to modify your queries.

SolrJ

  • SolrJ now supports the shards.preference parameter for single-shard scenarios to ensure multi-shard and single-shard request routing works in the same way.

  • QueryResponse.getExplainMap() type has changed from Map<String, String> to Map<String, Object> in order to support structured explanations.

    This change is expected to be mostly back-compatible. Compiled third-party components will work the same due to type erasure, but source code changes may be required.

  • Replica routing code has been moved to SolrJ, making those classes available to clients if necessary.

Streaming Expressions

  • A new DBSCAN clustering streaming evaluator has been added.

  • The precision stream evaluator can now operate on matrices.

  • The random streaming expression can now create the x-axis.

JSON Facets

  • Two new aggregations have been added: missing and countvals.

  • Several aggregations now support multi-valued fields: min, max, avg, sum, sumsq, stddev, variance, and percentile.

Caches

  • After the addition of CaffeineCache in 8.3, legacy SolrCache implementations are deprecated and likely to be removed in 9.0.

    Users are encouraged to transition their cache configurations to use org.apache.solr.search.CaffeineCache as soon as feasible.

Solr 8.3

See the 8.3 Release Notes for an overview of the main new features of Solr 8.3.

When upgrading to 8.3.x users should be aware of the following major changes from 8.2.

JWT Authentication

JWT Authentication now supports multiple identity providers. To allow this, the parameter jwkUrl has been deprecated and replaced with jwksUrl. Implementations using jwkUrl will continue to work as normal, but users should plan to transition their configurations to use jwksUrl instead as soon as feasible.

Caches

  • Solr has a new cache implementation, CaffeineCache, which is now recommended over other caches. This cache is expected to generally provide most users lower memory footprint, higher hit ratio, and better multi-threaded performance.

    Since caching has a direct impact on the performance of your Solr implementation, before switching to any new cache implementation in production, take care to test for your environment and traffic patterns so you fully understand the ramifications of the change.

  • A new parameter, maxIdleTime, allows automatic eviction of cache items that have not been used in the defined amount of time. This allows the cache to release some memory and should aid those who want or need to fine-tune their caches.

See the section Caches and Query Warming for more details about these and other cache options and parameters.

Solr 8.2

See the 8.2 Release Notes for an overview of the main new features of Solr 8.2.

When upgrading to 8.2.x, users should be aware of the following major changes from v8.1.

ZooKeeper 3.5.5

Solr 8.2 updates the version of ZooKeeper included with Solr to v3.5.5.

It is recommended that external ensembles set up to work with Solr also be updated to ZooKeeper 3.5.5.

This ZooKeeper release includes many new security features. In order for Solr’s Admin UI to work with 3.5.5, the zoo.cfg file must allow access to ZooKeeper’s "four-letter commands". At a minimum, ruok, conf, and mntr must be enabled, but other commands can optionally be enabled if you choose. See the section Configuration for a ZooKeeper Ensemble for details.

Until 8.3, SOLR-13672 causes the ZK Status screen in the Admin UI to not be able to report status. This only impacts the UI, ZooKeeper still operates correctly.

Routed Aliases

  • Routed aliases now use collection properties to identify collections that belong to the alias; prior to 8.2, these aliases used core properties.

    This is backward-compatible and aliases created with prior versions will continue to work. However, new collections will no longer add the routedAliasName property to the core.properties file so any external code depending on this location will need to be updated.

  • Time-routed aliases now include a TRA infix in the collection name, in the pattern <alias>_TRA_<timestamp>.
    Collections created with older versions will continue to work.

Distributed Tracing Support

This release adds support for tracing requests in Solr. Please review the section Distributed Tracing for details on how to configure this feature.

Solr 8.1

See the 8.1 Release Notes for an overview of the main new features of Solr 8.1.

When upgrading to 8.1.x, users should be aware of the following major changes from v8.0.

Global maxBooleanClauses Parameter

  • The behavior of the maxBooleanClauses parameter has changed to reduce the risk of exponential query expansion when dealing with pathological query strings.

    A default upper limit of 1024 clauses is now enforced at the node level. This was the default prior to 7.0, and it can be overridden with a new global parameter in solr.xml. This limit will be enforced for all queries whether explicitly defined by the user (or client), or created by Solr and Lucene internals.

    An identical parameter is available in solrconfig.xml for limiting the size of queries explicitly defined by the user (or client), but this per-collection limit will still be restricted by the global limit set in solr.xml.

    If your use case demands that you a lot of OR or AND clauses in your queries, upon upgrade to 8.1 you may need to adjust the global maxBooleanClauses parameter since between 7.0 and 8.1 the limit was effectively unbounded.

    For more information about the new parameter, see the section maxBooleanClauses.

Security

  • JSON Web Tokens (JWT) are now supported for authentication. These allow Solr to assert a user is already authenticated via an external identity provider, such as an OpenID Connect-enabled IdP. For more information, see the section JWT Authentication Plugin.

  • A new security plugin for audit logging has been added. A default class SolrLogAuditLoggerPlugin is available and configurable in security.json. The base class is also extendable for adding custom audit plugins if needed. See the section Audit Logging for more information.

Collections API

  • The output of the REQUESTSTATUS command in the Collections API will now include internal asynchronous requests (if any) in the "success" or "failed" keys.

  • The CREATE command will now return the appropriate status code (4xx, 5xx, etc.) when the command has failed. Previously, it always returned 0, even in failure.

  • The MODIFYCOLLECTION command now accepts an attribute to set a collection as read-only. This can be used to block a collection from receiving any updates while still allowing queries to be served. See the section MODIFYCOLLECTION for details on how to use it.

  • A new command RENAME allows renaming a collection by setting up a one-to-one alias using the new name. For more information, see the section RENAME.

  • A new command REINDEXCOLLECTION allows indexing existing stored fields from a source collection into a new collection. For more information, please see the section REINDEXCOLLECTION.

Logging

  • The default Log4j2 logging mode has been changed from synchronous to asynchronous. This will improve logging throughput and reduce system contention at the cost of a slight chance that some logging messages may be missed in the event of abnormal Solr termination.

    If even this slight risk is unacceptable, the Log4j configuration file found in server/resources/log4j2.xml has the synchronous logging configuration in a commented section and can be edited to re-enable synchronous logging.

Metrics

  • The SolrGangliaReporter has been removed from Solr. The metrics library used by Solr, Dropwizard Metrics, was updated to version 4, and Ganglia support was removed from it due to a dependency on the LGPL license.

Browse UI (Velocity)

Default Garbage Collector (GC)

  • Solr’s default GC has been changed from CMS to G1. If you prefer to use CMS or any other GC method, you can modify the GC_TUNE section of solr.in.sh (*nix) or solr.in.cmd (Windows).